The four dimensional space, means that the mankind the substance space( namely three dimensional space ) of the concrete activity, plus one more consciousness measurement ( time factor).

四维空间，是指在人类具体活动的实质空间（即三维空间）之上，再加上一个瞬间取向的知觉量度（即时间因素）。

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Another possibility is that the accelerated expansion arises not from a substance but from a modified form of gravity, one that behaves differently on cosmic scales of time and space.

另一种可能性是加速膨胀不是来自物质而是修改的重力形式，其作用在时空的宇宙尺度上是不同的。

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Scientists are working to discover new applications for the substance, ranging from the next generation of tennis rackets to super-insulated space suits for a manned mission to Mars.

科学家们正在继续尝试发现这种物质的新用途，可能的应用领域从新一代的网球拍直至载人火星任务使用的超级隔热的宇航服。

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Scientists at the Goddard Space Flight Center in Greenbelt,Maryland, found the substance glycine in material brought back to Earth from a comet.

VOA: special.2009.09.30

When opened and closed, these blinds--coated with a gravity-defying substance--initiate man's voyage into space.

FORBES: Eerily Prescient

The space agency revealed earlier this year that it was studying using the substance to create a new kind of black paint.

BBC: Carbon nanotubes experiment results